American scientists are investigating whether Pfizer's latest Covid booster might be increasing the risk of stroke in some people aged over 65 after a possible link was flagged up between the updated dose and a higher risk of "ischemic" in the three to four weeks after vaccination.
Officials from the Centres for Disease Control and Prevention and the US Food and Drug Administration said other systems that are used to track vaccine outcomes have not established a similar link, leading them to conclude this may be an anomaly rather than a cause for alarm.
However, in a joint statement from the CDC and FDA experts said: "It is very unlikely that the signal would represent a true clinical risk, we believe it is important to share this information with the public." The agencies have issued similar statements in the past, when a safety monitoring system detects a signal.
